さて、私はこれらを試しましたが、どれも機能していないようです。私の例の文字列は
$text_description=" Hello world! lorel ipsum";
$text_description= str_replace(" "," ",$text_description);
$text_description = preg_replace("/&#?[a-z0-9]+;/i"," ",$text_description);
$text_description=html_entity_decode($text_description);